1. Field of the Invention
The present invention relates to a heat pump, and, more particularly, to a heat pump having an accumulator inlet side introducing pipe extending through a discharge pipe of a compressor in order to prevent the compressor from being damaged due to low-temperatures and low-pressure liquid refrigerant passing through an outdoor heat exchanger into a compressor, thereby preventing liquid refrigerant from entering into the accumulator and the compressor, maintaining the compressor discharge pressure to a predetermined pressure level, when the temperature of outdoor air is low or the load is excessive, to stabilize the compressor suction pressure, and control the liquid-compression phenomenon, when the outdoor heat exchanger is covered with frost as the temperature of the outdoor air is lower in winter, and therefore, no evaporation process is performed, to prevent the compressor from being damaged.
Also, the present invention relates to a compressor discharge pressure control apparatus for such a heat pump that is capable of decreasing the pressure and temperature of refrigerant discharged from the compressor to a set pressure and temperature levels, when the cooling load or heating load is excessive, to uniformly maintain the compressor discharge pressure and compressor suction pressure.
2. Description of the Related Art
FIG. 1 is a view schematically showing the structure of a conventional heat pump.
As shown in FIG. 1, the conventional heat pump comprises: a compressor 10 for compressing refrigerant into high-temperature and high-pressure gas refrigerant in a heating operation mode; a condenser, i.e., an indoor heat exchanger 20 for performing heat exchange between the refrigerant compressed by the compressor 10 and air (if the heat pump is an air-cooled type heat pump) to condense gas refrigerant into liquid refrigerant; an expansion valve 30 for expanding the high-temperature and high-pressure liquid refrigerant condensed by the indoor heat exchanger 20 into low-pressure gas refrigerant by a throttling expansion action; an outdoor heat exchanger 40 for evaporating the refrigerant expanded by the expansion valve 30, performing heat exchange between the refrigerant and air blown by a blower through the use of the latent heat of vaporization of the refrigerant to cool the air, and returning the gas refrigerant to the compressor 10; and an accumulator 50 for separating the refrigerant collected from the outdoor heat exchanger 40 into liquid refrigerant and gas refrigerant to supply only the gas refrigerant to the compressor 10.
In the heat pump, the accumulator 50 serves to separate the refrigerant evaporated by the outdoor heat exchanger 40 into liquid refrigerant and gas refrigerant such that only the gas refrigerant is introduced into the compressor 10. In addition, the accumulator 50 serves to prevent the liquid refrigerant from entering into the compressor 10 such that the compressor 10 prevented from being damaged due to compression of the liquid refrigerant.
While refrigerant is circulated in the heat pump, gas refrigerant is changed into liquid refrigerant, and then the liquid refrigerant is changed into the gas refrigerant. A switching operation between heating operation mode and cooling operation mode is performed by a four-way valve 60 in the heat pump. The heat pump is a system that produces high-temperature heating sources as sources necessary for performing a heating operation.
In the conventional heat pump, however, it is difficult to produce such high-temperature heating sources. Although high-temperature heating sources are produced by the conventional heat pump, the amount of heating sources is very small. Also, the high-temperature heating sources are intermittently produced by the conventional heat pump. As a result, when the temperature of the outdoor air is decreased in winter, the performance of the heat pump sharply deteriorates, and therefore, the temperature of heating sources is lowered. Furthermore, evaporation pressure and specific volume of refrigerant introduced into the compressor are increased, and therefore, pressure ratio, which is the ratio of compressor discharge pressure to evaporation pressure, is increased. Consequently, compression efficiency of the heat pump is lowered, and the compressor temperature is excessively increased, which causes the compressor to be damaged. Especially, the condenser is operated at high temperature and high pressure to produce a high-temperature heating source, and therefore, excessive load is applied to the compressor. As a result, the compressor is damaged.
Furthermore, the performance of the heat pump is sharply deteriorated, and the operation power of the compressor is increased as the evaporation pressure is lowered and the condensation pressure is increased. Consequently, the compressor is damaged, and the energy consumption of the heat pump is increased. When the temperature of outdoor air is decreased in winter, the evaporation temperature is low, and therefore, the specific volume and efficiency are decreased. Consequently, the performance of the heat pump is lowered, and the energy consumption of the heat pump is increased. Especially in the conventional heat pump, the compression ratio, which is the ratio of condensation pressure to evaporation pressure, is increased when the temperature of the outdoor air is decreased. As a result, the compression efficiency of the compressor is lowered, and therefore, the performance of the heat pump is lowered.
In the conventional heat pump, the compressor discharge pressure and temperature are excessive when the load is excessive, and therefore, the compressor is damaged.